Disclaimer: I loved the first three movies when they first came out, and expected the prequels to be better story-wise (the effects much better of course). However, growing up you realize we like this movies because of the way the affected us when we were young, not because they are truly good.
Forget about Luke being Leia's sister as an add-on story in Episode VI after the other two have already developed. I hated that even then - bad storytelling. Episode I-III try to follow up on that story and get a better continuity, but still they are not good movies.
The whole Sith vs. Jedi concept is wrong in the practical sense. C'mon: 20+ jedis, Yoda included, were unable to notice Palpatine was the Sith Lord AND at the same time they treat Anakin as an asshole, which eventually makes him turn to the dark side. Their attitude is so moronic they DESERVED to be exterminated by only two siths (although it was just Sidious really, Anakin was too young).
In general, The Sith "business model" of having only two guys is very fragile: one dies and you do not have anybody to replace him with. When Darth Sidious lets Anakin kill Count Dooku to take his place is really stupid: You should keep both of them if both are good enough. This lets you do twice as much, or two things at the same time. Makes for bad stability of your empire. Who can you trust?
Another analysis lets you know the jedis should have won the war hands down, it not by sheer numbers, but they were unable to see the danger lurking in the dark side, even though having it right in front of them. This tells you the dark side is much much powerful, or again, they were truly dumb.
You see this same fragility in Ep VI. If Vader had not turned against Sidious, they could have ruled for some more time. Sidious was much too powerful for both Vader and Luke, but his "lack of vision" did not allow him to see that they were both family, or "sense" Vader might have turned against him, or whatever.
I could go on but you get the point. Fantastic movies when you're 13. I am not looking forward to more SW movies that don't have logic in their characters. However, Disney might do a better job than Lucas.